1. Field of the Invention
The present invention relates to a rotary polygonal mirror suitable for use in laser scanning systems and other optical systems and a method of making such a polyhedral mirror.
2. RELATED BACKGROUND ART
The rotary polygonal mirror is mounted in an optical system of the laser scanner, for example, such that a path of laser beam will be changed for causing the laser beam spot to scan a light receiving surface. A rotary polygonal mirror is typically known which is of an equilaterally polygonal cross-section such as a regular hexagon with all the sidewalls thereof being reflective.
Such a rotary polygonal mirror is conventionally produced by forming a body of optical glass into an equilateral polygonal member through grinding polishing and other steps and finally polishing the sidewalls of the member to provide reflective mirror faces, or alternatively by first cutting an equilateral polygonal member from a material of metal such as aluminum alloy and the like and then subjecting the member to an ultra-precision machining to form reflective sidewalls by the use of a diamond cutting tool.
However, the aforementioned processes of making the rotary polygonal mirror have a great number of steps and particularly require an increased amount of labor and time. Moreover, the process requires a high degree of technology in cutting mirror blanks from the optical glass or metallic material and forming them into rotary polygonal mirrors having accurately reflective side faces through grinding, polishing and other machining operations. Further, if a rotary polygonal mirror having a complicated configuration other than its reflective mirror faces is to be formed, even more complicated technology and greater number of steps are required leading to increased cost of manufacturing.
Another problem also exists when a heavy material such as optical glass or metal is to be used to form a mirror blank, i.e., the entire weight of a rotary polygonal mirror constructed of such a mirror blank cannot be decreased as desired.